1. Field of the Invention
The invention relates to piston rings, and more precisely, to piston rings for internal combustion engines and methods of forming the same.
2. Related Art
Recent development of internal combustion engines has resulted in increased compression pressures within the combustion chamber of engines and increased engine speeds. As a consequence, the piston rings on the pistons of such engines are rubbed more forcefully against the cylinder walls of the engine, which could result in excessive wear occurring on the exterior of an unprotected piston ring thereby leading to a weaker seal between the piston and the cylinder wall.
Piston rings for internal combustion engines are typically formed of cast iron or steel materials. One process for reinforcing a cast iron or steel ring is to apply a layer of pure chromium around at least the outer diameter surface of the piston ring. This is advantageous because the chromium directly engages the cylinder wall and protects the cast iron or steel from rubbing or sliding contact with the cylinder wall. Another known process is to apply a layer of less than 70 wt. % cobalt and the remainder of chromium onto the outer diameter surface of piston rings. In such coatings, the chromium provides the primary wear protection, and the cobalt acts as a binder for the chromium.